People write them. There are sites that have most of the code for same already written so people can just plug in ideas (and I should finish the ones I'm writing). Others of them start as things written in someone's journal and a bunch of other people think it's a neat idea and go from there, and so on.
I suspect the latter would be bandwidth-intensive. Though there are a number of things that will pull data from the last fifty public entries and manipulate it (such as the mood pie -- I have a mood pie posted in my userinfo if you have no idea what I'm talking about); that might be something someone could play with. Though the music postings don't tend to have an especially standard formate.
![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
timeasmymeasure
no subject
I suspect the latter would be bandwidth-intensive. Though there are a number of things that will pull data from the last fifty public entries and manipulate it (such as the mood pie -- I have a mood pie posted in my userinfo if you have no idea what I'm talking about); that might be something someone could play with. Though the music postings don't tend to have an especially standard formate.